In underground drilling applications, such as oil and gas or geothermal drilling, a borehole is drilled through a formation deep into the earth. Such boreholes are drilled or formed by a drill bit connected to the end of a series of sections of drill pipe, so as to form an assembly commonly referred to as a “drill string”. The drill string extends from the earth's surface to the bottom of the borehole. As the drill bit rotates, it advances into the earth, thereby forming the borehole. In order to lubricate the drill bit and flush cuttings from the drill bit's path as it advances, a high pressure fluid, referred to as “drilling mud”, is directed through an internal passage in the drill string and out through the drill bit. The drilling mud then flows to the surface through an annular passage formed between the exterior of the drill string and the surface or interior wall of the borehole.
The distal or bottom end of the drill string, which includes the drill bit, is referred to as a “downhole assembly”. In addition to the drill bit, the downhole assembly often includes specialized modules or tools within the drill string that make up an electrical system for the drill string. Such modules often include sensing modules. In many applications, the sensing modules provide the drill string operator with information regarding the formation as it is being drilled through, using techniques commonly referred to as “measurement while drilling” (MWD) or “logging while drilling” (LWD). For example, resistivity sensors may be used to transmit and receive high frequency signals (e.g., electromagnetic waves) that travel through the formation surrounding the sensor.
As can be readily appreciated, such an electrical system may include many sophisticated electronic components, such as the sensors themselves, which in many cases include printed circuit boards. Additional associated components for storing and processing data in the control module may also be included on printed circuit boards.